ARCHIVED REPORTS XR0001402 - Laserfiche WebLink

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• Subsurface soils in the vicinity of the Site are primarily comprised of silt and clay to at least 50 feet • Initial groundwater, situated in the clayey matrix, was typically observed at a depth of 30 to 35 feet Groundwater is slow to yield, but typically rises under confined pressure to about 23 to 25 feet • Groundwater flows east-southeast at a gradient of about 0 0026 ft/ft • BTEX concentrations in soil samples collected above the groundwater table are relatively low compared to those obtained below Higher BTEX concentrations in soil samples collected below the groundwater table may be a result of the contaminated groundwater present within their matrix 0 TPHg concentrations in soil samples collected above the groundwater table are relatively higher compared to those obtained below BTEX concentrations, once potentially present in these higher TPHg-impacted soil samples, appear to have degraded • The lateral extent of petroleum impacted soil appears to be narrowly confined in the vicinity of the former UST The vertical extent of impact is evaluated to be 50 to 55 feet • Oxygenate compounds have not been detected in any soil sample • BTEX and TPHg concentrations in groundwater at the MW-2 location are relatively high O BTEX and TPHg concentrations in groundwater at the MW-1, MW-3, MW-4 and PH-8 locations arc relatively low or were not detected U BTEX and TPHg concentrations in groundwater at the PH-6 and PH-7 locations may be a result of previous retail gasoline operations at the 1725 El Dorado Street property • Oxygenate compounds TBA, MTBE and DIPE have been detected sporadically in groundwater samples 1.3 Current Groundwater Conditions Philip performed groundwater monitoring at the Site most recently on June 27, 2002 As summarized in Table 1 (Groundwater Elevation Data), groundwater was measured in wells MW-1 through MW-4 at depths ranging from 25 24 feet to 26 10 feet Recent elevation data indicates that groundwater flow is easterly and at a similar gradient as measured in previous rounds of monitoring (see Figure 3) As summarized in Table 2 and shown in Figure 4, BTEX and TPHg concentrations remain relatively high in the samples collected from well MW-2 BTEX and TPHg concentrations are non- detectable or relatively low in samples collected from wells MW-1, MW-3 and MW-4 Laboratory reports are contained in Appendix A 6 Pilot Testing Work Plan 1717 South Center Street-Stockton,California Prepared by Philip services Corp K\ENVW2400132%1213$2EG5Projoml SlockCentlptlottm(plan doc July 23,2002